This invention relates to a control system for controlling the position of a crop discharge spout on an agricultural machine (such as a forage harvester) with relation to a crop-receiving wagon.
It is known to automatically align the crop discharge spout of a forage harvester with respect to the tongue of a trailing crop-receiving wagon to reduce crop spillage. Such systems are described in U.S. Pat. No. 3,786,945 and in U.S. Pat. No. 4,042,132. Another such system, utilizing electro-optical devices, is described in British patent application GBT No. 2073914, published Oct. 21, 1981. However, the operation of such optical devices could be adversely affected by the large amount of dirt and debris usually present in the vicinity of a forage harvesting machine. The system described in the published British application includes an offset device which is comprised of an adjustable potentiometer. It is suggested therein that this potentiometer can be manually adjusted to achieve better side-to-side distribution of material in the collector vehicle. However, a system which would automatically provide even wagon filling has long been desired. This published British application recognizes this fact and suggests that "an automatic readjustment may be applied to produce a periodically altering position programmed in a specific manner", and further suggests that ". . . it may be desired slowly to dither or oscillate the discharge spout to achieve a better side-to-side distribution . . .". However, this British publication does not disclose any means by which such desired automatic functions could be achieved.
It has been suggested that even wagon filling can be obtained by continuously sweeping the spout back and forth in an oscillatory manner. However, such continuous sweeping requires large amounts of energy and would increase the rate of wear of the mechanical or hydraulic components.
It is also known to maintain the spout within distinct wide and narrow ranges, depending upon whether the forage harvester is traveling straight or is executing a turn, as shown in U.S. patent application, Ser. No. 282,364, filed July 13, 1981 now U.S. Pat. No. 4,401,403 and in U.S. patent application Ser. No. 347,125, filed Feb. 9, 1982, now U.S. Pat. No. 4,441,846 both assigned to the assignee of the present invention. All these aforementioned systems utilize analog and discrete component circuitry and thus, their functional complexity is limited by cost considerations. Furthermore, although these systems help to prevent crop spillage, they do not provide automatic even wagon filling because, while in straight line travel, the spout may spend a majority of the time directing crop to one side or the other of the wagon. Therefore, it is desirable to make use of advanced electronics technology to overcome this problem and to implement other desired spout-aiming control functions.